Fin-propelled watercraft

ABSTRACT

A floating body is operable to rock about a predetermined axis. A torsion-elastic fin stem is mounted on the floating body and substantially intersects the axis and has a free end portion extending from this body. A fin is secured to the free end portion and adapted to produce a thrust in response to a rocking motion of the body about the axis.

I Umted States Patent [151 3,646,240 Stein 51 Feb. 3, 1972 [54]FIN-PROPELLED WATERCRAFT 3,453,981 7/1969 Gause ..115/28 X 3,358,63612/1967 Curtiss et al. ..115/28 [72] Inventor: Erich Stein, 2,Josef-Graber-Gasse, A-

5020 salzburg Ausma Primary ExaminerAndrew H. Farrell 22] Filed: Oct.23, 1969 ROSS [21] Appl No.: 868,771 [57] ABSTRACT A floating body isoperable to rock about a predetermined Foreign Application Priority Dataaxis. A torsion-elastic fin stem is mounted on the floating body andsubstantially intersects the axis and has a free end portion 2: 2extending from this body. A fin is secured to the free end porp tion andadapted to produce a thrust in response to a rocking 52] U S CI 115/28motion of the body about the axis. [51] Int. Cl ...B63h U36 5 Claims, 15Drawing Figures [58] Field of Search ..l15/2830 [56] References CitedUNITED STATES PATENTS Jonsson ..1 15/28 X brick. INVENTOR aw mar sum 20F 2 FIN-PROPELLED WATERCRAFT SUMMARY OF THE INVENTION The inventionrelates to awatercraft, which is propelled by movable fins. For thispurpose, the fin or fins are secured to one end of a torsion-elastic finstem, which substantially intersects the axis about which the fins canrock. In one embodiment, the fin stem is or the fin stems are rigidlyconnected to the hull of the vehicle and the watercraft is propelled bybeing rocked about a natural axis of oscillation. This may beaccomplished by the user of the watercraft, who stands with spreadapartlegs on the watercraft and alternately angles one leg and the other toimpart a rocking motion to the watercraft. The fin stem or fin stems maybe, alternatively, arranged to rock about an artificial axis ofoscillation, which is substantially parallel to the longitudinal axis ofthe hull of the craft. In this case, motion can be imparted to the hullof the vehicle by a pivotal movement of the stem of the fin. The firrorfins may consist of rigid members and are suitably substantiallystreamlined. Alternatively, they may consist of resilientlyflexibleblades.

Where a pivoted fin stem is or pivoted fin stems are used in oneembodiment, that portion of the fin stem which lies within the hull ofthecraft may be provided with an upstanding hand lever. In anotherembodiment, that portion of the fin stem which lies within the hull ofthe craft may be connected to a substantially horizontal treadle plate.

It will be suitable to stiffen the fin stern transversely to the planein which the fins are in position of rest.

DESCRIPTION OF THE DRAWING In the drawing:

FIG. 1 is a side elevation showing an embodiment of the invention inwhich a flexible fin is secured to a fin stem which 'is rigidlyconnected to the hull of the craft.

FIG. 2 is a front elevation showing the watercraft of FIG. 1 inoperation.

FIG. 3 is an enlarged cross-sectional view taken on line III In in FIG.1.

FIG. 4 is an enlarged transverse sectional view taken through the fin online IV-IV in-FIG. 1.

FIG. 5 shows a modification of the watercraft of FIG. 1 with an obliquefin stem extending obliquely laterally and rearwardly.

FIG. 6-is a transverse sectional view showing a modified fin whichconsists of a rigid streamlined body.

FIG. 7 is a transverse sectional view taken on line VII-VII of FIG. 8and showing a modified embodiment having a'movable fin stem.

FIG. 8 is a fragmentary longitudinal sectional view taken on lineVIII-VIII in FIG. 7. e

FIG. 9 is a sectional view taken on line IX-IX in FIG. I0 and showing acanoe embodying the invention and having two angled, rigid fin stems.

FIG. 10 is a side elevation of the canoe according to FIG. 9.

FIG. 11 is a diagrammatic transverse sectional view showing areciprocating piston for driving the movable fin stern.

FIG. 12 is a side elevation showing a watercraft embodying the inventionand comprising two finned and nonpivoted fin stems, one of which can berotated about its longitudinal axis and fixed in osition.

, FIG. 13 is an enlarged view showing a detail of FIG. 12.

FIG. 14 shows a surfboard which is provided with a fin ac cording to theinvention.

FIG. 15 is a side elevation showing another embodiment of the inventionin a watercraft which comprises two fins, one of which is small andmovably mounted on the hull whereas the other is arranged on a fin stem,which is pivotally movable about a substantially horizontal axis whichis substantially at right angles to the longitudinal axis of thevehicle.

SPECIFIC DESCRIPTION In the first embodiment shown in FIGS. 1, 2, 32nd4, the

guide passage for the fin stem 2 extends through the hull. The finsternconsists of hardwood and a steel strip 6, which is insertecl in andfirmly adhesively bonded to the wood in the highlystressed portionbetween the hull 1 and the fin 3. This strip will prevent a substantiallateral deflection of the stem. 0n the other hand, the stem can beresiliently twisted about its longitudinal axis. A wing screw 4 clampsthe stem in a bushing 7, which forms an extension of the guide passageat the top end thereof. When a person stands on the hull l, which floatsin the water, and more weight is applied to the left-hand side of thehull in FIG. 2, as is shown there, the hull will be inclined to the leftand the fin 3 will be moved to the right about the natural horizontalaxis of oscillation A-B. The resistance presented to the fin 3 by thewater will cause the fin stem 2 to be slightly twisted and the fin 3 tobe pivotally moved about the torsion axis C-D of the fin stem; thetorsion axis C-D is at right angles to the axis AB. This causes the finto assume an oblique position relative to the direction of travel. Theresilient end of the fin is rearwardly deflected at the same time sothat the wateris displaced to the rear. The fin 3 is suitably somewhatharder at the lower edge than at the upper edge because the lower edgemoves somewhat faster so that it encounters a larger resistance by thewater. Unless the lower edge were harder, it would be more highlydeflected to the rear and the water would be partly displaced downwardlyrather than to the rear.

Because of the resistance encountered by the fin 3, the hull 1 isinclined so slowly that the person standing thereon has time to load theother side so that the fin 3 is deflected. The person stands desirablywith his two feet on respective slipproof treads 5 and 5a, which areraised like wedges toward the outside, and may hold himself at theupwardly protruding end portion of the fin stem 2. When the wing screw 4has been released, the depth of the fin 3 can be adjusted and the finstem 2 can be pulled out entirely when the watercraft is to betransported. The watercraft can be climbed upon from the water withoutdifficulty. It has a very good response to steering actions performed bya shifting of weight so that there is no need for a steering devicealthough the craft can be provided with such device in a simple manner.

The embodiment shown in FIG. 5 has a fin stem 2, which is secured tothetip of the hull l and extends obliquely in a lateral 'and downwarddirection. The fin stem 2 does not include a steel strip so that thestem will be laterally deflected and twisted if the fin 3 is caused, tooscillate under water about a horizontal axis A-B. In the same manner, asecond pivotal movement is produced, which causes the fin 3 to extend atan obliqueangle to the direction of travel but which is notperformeda'bout an exactly defined axis.

Instead of a resilient fin, a rigid fin 3 consisting of a streamlinedmember as shown in FIG. 6 may be used to drive the craft.

In the embodiment shown in FIGS. 7 and 8, the twistable fin stem 2ispivotally movable by means of an articulated joint about a horizontalaxis. For this purpose, a bearing 11 for a rotatable shaft 17 isarranged in a trough-shaped recess 12 in the bottom of the hull 1. Thisshaft 17 extends outwardly through a horizontal opening at the end ofthe trough-shaped recess'. The fin stem 2 is secured to the shaft 17 atthe portion thereof which is outside the recess. Two brackets 13 for atreadle plate 14 are rigidly connected to the shaft 17. An arm lever 15is secured to the forward bracket 13. A person who desires to use theboat stands with slightly spaced-apart legs on the treadle plate 14 andshifts his weight so that the plate 14 is altematingly tilted to theright and left and the fin stem 2 is pivotally moved into the respectiveopposite direction. The rubber bufi'ers 16 mounted on the treadle plate14 avoid any hard impact of the treadle plate 14 on the floor of theboat. The arm lever 15 may be used to assist the work of the legs or theboat may be propelled by the arms alone so that it does not rock.

FIGS: 9'and 10 show how a canoe may be provided with hull l of thewatercraft is completely closed on all sides and a propelling finsaccording to the invention. Two wedge-shaped treads 5 are secured besidethe seat hatch. A mounting 19 for a crossbar 18 is secured to theforward end of each tread. A fin stem 2 is secured to each end of thecrossrod l8 and has an angled portion followed by a much slendererportion. The fin stem 2 carries at its lower end a fin 3. Owing to theangled portion of the fin stems 2, one of the end portions of the fins 3is directed exactly to the axis of oscillation A-B of the boat. Theslender portions of the fin stems 2 below the angled portion can beresiliently twisted whereas the thick portions above the angled portionyield only to a small extent.

The watercraft shown in FIG. 11 is driven by a steam engine. A steamboiler, not shown, discharges steam into the cavity 58 under a gatevalve 56, which opens a flow path into one of the steam passages 57.From the latter, the steam enters the right-hand chamber of a cylinder46 to force a piston 47 against the other end of the cylinder. Thepiston rod 48 is moved by the piston 47 and at its end carries a pin 49,which is received by a slot 50 formed in a lever 51 so that the lattermoves the fin stem 2 by means of an articulated joint 17. A second pin53 slides in a second slot 52 of the lever 51 to move a rod 54 whichcontrols the gate valve 56. A guide 55 holds the rod 54 parallel to thepiston rod 48. When the piston 47 reaches the other end of the cylinder46, the control rod 54 pulls the gate valve 56 to the other side so thatsteam can flow into the left-hand chamber of the cylinder 46 and steamcan escape from the right-hand chamber. In this way the watercraft canbe moved forwardly without need to transform the linear piston movementinto a rotary movement. Instead of pressurized steam, other gases orliquids may be used as a source of power.

In the embodiment shown in FIGS. 12 and 13, a tube 31 is disposed in thehull l of the watercraft and the fin stem 2 of a rear fin 3 extendsthrough that tube. The upper end of the tube 31 is closed by a metalbush 32, which is firmly connected to the tube. As in the precedingembodiments, a wing screw 4 is mounted at the top end of the tube 31 toclamp the fin stem 2 so that it has the desired elevation. The upperflange 20 of the bush 32 is formed with grooves 21, which are spacedapart and which can receive a spring 33 to prevent a rotation of thebush 32, the tube 31 and the fin stem 2. The lower end flange 22 of thebush 31 is formed with a groove 23, which receives an inner spring 34when the fin 3 is in its normal position for a straight-on travel of thecraft. The spring 34 is connected to the first spring 33. The twosprings 33 and 34 are shown in a snapped-in condition and secured to areinforcing member 24 of the deck. The end of the inner spring 34 formsa hook 25, which embraces the outer spring 33. The end of the latterfonns an eye 26, to which a rope 35 is tied. A hand lever 36 isconnected to the upper part of the fin stem 2 and is fixed by means of awing screw 37. A short transverse spar 27 is secured to the free end ofthe hand lever 36 to form a T therewith and provides a handle, which canwell be gripped by both hands. The other end of the rope 35 is tied tothe transverse spar 27.

The rope 35 is pulled when it is desired to change the direction oftravel. This will first pull the upper spring 33 out of its groove 21.As the pull on the rope is continued, the spring 33 engages the hook 25of the spring 34 to pull the latter out of the groove 23 in the lowerflange. When the swing is now discontinued for some time, the hand lever36 can be operated to move the fin 3 easily into the posiu'on which isrequired for a travel of the craft along a bend having the desiredradius. The rope 35 is then released so that the spring 33 snaps intoone of the grooves 21 associated with it. This is important becauseduring the swing the water pressure acting on the fin 3 is so high thatit cannot be held well in the desired position by the hand lever 36.When the craft has completed the travel along the arc, the rope 35 ispulled once more to withdraw the spring 33 from the groove. The pullshould not be so strong that the lower spring 34 is also withdrawn fromthe flange 22. As the hand lever 36 is returned to its normal position,the lower spring 34 slips on the flange 22 and automatically snaps intothe correct position. The rope 35 can then be released.

When it is desired to travel along an arc to the right, the two springs34 and 33 may be pulled out of the grooves 23 and 21 when the boat isbeing rocked from the left to the right. The water pressure will thencause the fin 3 to swing to the right and the spring 34 may be allowedto fall in when the fin 3 has reached the desired position. Similarly,the fin 3 can easily be moved to its normal position when the boat isbeing rocked from the right to the left and the spring 33 is pulled outof the groove at the same time and the spring 34 is allowed to slip onthe flange 22 until it snaps into position to lock the fin. The handlever 36 need not be touched throughout this maneuver and could even beomitted. On the other hand, the hand lever 36 is of great help when thewatercraft is to be turned round while it is not traveling. For thisoperation the two springs 34 and 33 are pulled out of the grooves andthe hand lever 36 is used to pivotally oscillate the fin 3 approximatelybetween angles of 60 and relative to the normal position so that the fin3 produces a thrust which acts transversely on the rear end of thewatercraft and causes the latter to turn about the forward fin 3. Areverse travel is also possible if the fin 3 is swing through as much asThe reverse travel is slightly impeded by the forward fin 3.

In addition to an extreme directional stability, the watercraft in thisembodiment thus has a very high maneuverability.

FIG. 14 shows how a surfboard 42 can be propelled with the aid of a fin3. The fin stem 2 is rotatably mounted on a horizontal transverse pin 40and can be pivotally moved to the rear into a horizontal position, inwhich it is received by a groove 43, which extends on the underside ofthe surfboard 42 from the slot to the rear end. In this position the fin3 extends upwardly behind the surfboard and does not disturb thesurfrider. A short hand lever 38 may be used to swing the fin stem 2 andis also received by a groove 44 formed on the upper side. A protrudingnose 45 at the fin stem 2 forms the rigid steering fin, which is usualwith conventional surfboards. When the fin 3 has been swung down, thesurfboard can be propelled by a rocking motion so that the surfrider cantravel out against the surf and then ride back on a wave although theflat surfboards are not so well suited for fin propulsion, which in thiscase requires a greater effort. The groove 43 on the underside mayextend forwardly from the slot rather than rearwardly; in that case, thefin stem 2 is mounted to extend in the opposite direction so that thecraft when propelled by the fin travels in a direction which is oppositeto its direction when carried along by a wave.

In the embodiment shown in FIG. 15, the hull 1 has a slo which is aswide as the fin stem 2. The upper end portion of the latter forms alever 38. Near the upper end of the slot, two bearings are disposed onthe sides of the slot. A pin 40 extends through said bearings and can befixed in position. The fin stem 2 has a through bore and is rotatablymounted on the pin 40, which holds the fin stem in position so that themain fin 3 can be swung upwardly in forward and rearward directions.

When it is desired to disembark at or embark from a flat beech, thelever 38 is pushed forwardly as far as possible so that the main fin 3is swung up to the hull l and the craft can travel even in water havinga depth of about 50 centimeters. Whereas the watercraft does not have avery high stability with the fin in this position, it can still bebalanced. In deep water, the main fin 3 is adjusted to an intermediateposition, which is most desirable for fast propulsion. The main fin 3 isdesigned so that the thrust produced by it in that position has ahorizontal direction. A resilient tail fin 41 is connected to the hull land serves to stabilize the direction of travel. The tail fin 41produces only a small thrust because it is too close to the axis ofoscillation. Because the main fin 3 producing the major portion of thethrust is disposed before the center of gravity of the watercraft, thelatter is pulled by the main fin. The point where the resistancespresented by both fin surfaces to a lateral flow are balanced liesbehind the center of gravity so that the watercraft will not turn roundwhen the thrust is discontinued. In this case, the watercraft would turnround if the tail fin 41 were omitted. Slight changes in direction canbe induced by certain weight-shifting operations. To travel along asharp curve, the main fin 3 is swung forwardly as far as possible andthe change in direction is initiated at the same time. The point wherethe resistances presented by both fin surfaces to a lateral flow arebalanced is now disposed before the center of gravity so that thewatercraft travels along a sharp bend. A fast travel can be stoppedquickly in this way. When it is desired to turn round on the spot whilethe watercraft has no or only a slow speed, it will be swung to one sidewith the main fin 3 advanced and to the other side with the main fin 3directed rearwardly.

The main fin can be adjustably mounted with different means. Forinstance, the fin stem may be freely movable in a slot so that it can bepulled up or swung. Alternatively, a carriage could be provided, whichis displaceable in the longitutending from the bow to the stern;

an elongated stem extending downwardly from said body substantially inthe plane of and generally transverse to said axis at a locationintermediate said bow and said stern, said stem being secured to saidbody but having a lower free end resiliently twistable relative to saidbody; and

a fin attached to said free end at a forward portion of the said fin andwith spacing below said body, said fin having an edge proximal to saidbody of lesser stiffness than the edge of said fin distal from saidbody, said fin having a trailing portion resiliently deflectableindependently of said stem.

2. The watercraft defined in claim 1 further comprising dinal directionof the watercraft and in which the fin stem is means for mounting SaidStem movably Said y- 3. The watercraft defined in claim 1 wherein saidstem is provided with an extension, running above said body.

4. The watercraft defined in claim 1 wherein said stem converges towardsaid axis in the direction of the bow.

5. The watercraft defined in claim 1 wherein said stem projects fromsaid body perpendicularly to said axis.

1. A watercraft comprising: a floating elongated body having a bow and astern and adapted to rock about a longitudinal axis of the bodyextending from the bow to the stern; an elongated stem extendingdownwardly from said body substantially in the plane of and generallytransverse to said axis at a location intermediate said bow and saidstern, said stem being secured to said body but having a lower free endresiliently twistable relative to said body; and a fin attached to saidfree end at a forward portion of the said fin and with spacing belowsaid body, said fin having an edge proximal to said body of lesserstiffness than the edge of said fin distal from said body, said finhaving a trailing portion resiliently deflectable independently of saidstem.
 2. The watercraft defined in claim 1 further comprising means formounting said stem movably on said body.
 3. The watercraft defined inclaim 1 wherein said stem is provided with an extension, runNing abovesaid body.
 4. The watercraft defined in claim 1 wherein said stemconverges toward said axis in the direction of the bow.
 5. Thewatercraft defined in claim 1 wherein said stem projects from said bodyperpendicularly to said axis.